Brush macromolecules with thermo-sensitive coil backbones and pendant polypeptide side chains: synthesis, self-assembly and functionalization

Abstract

Macromolecular brushes with thermo-sensitive poly(N-isopropylacrylamide) (PNIPAM) backbones and pendant poly(γ-benzyl-L-glutamate) (PBLG) side chains were synthesized by reversible addition–fragmentation chain transfer (RAFT) and ring-opening polymerization (ROP). Copolymers of NIPAM and N-acryloxysuccinimide (NAS) were synthesized by RAFT polymerization. Boc-protected amino groups were introduced into the backbone chains by substituting the NAS groups with N-Boc-ethylenediamine, and after removal of the Boc groups, amine groups were produced on the backbones. PBLG side chains were synthesized by ROP. Size exclusion chromatograph, ¹H NMR and ¹³C NMR results indicated successful synthesis of well-defined brush macromolecules. The self-assembly of the macromolecules in aqueous solutions was investigated in this research. Depending on the backbone and side chain lengths, the brush macromolecules self-assemble into spherical micelles, worm-like structures and vesicles. Temperature exerted a significant effect on the morphology of the structures. At a temperature above lower critical temperature (LCST) of the PNIPAM backbone, the self-assembled structures aggregated together. The functionalization of PBLG side chains with 1-pyrenebutyric acid was also performed. The fluorescence properties and morphology of the functionalized brush macromolecules were investigated in this research.